In article transport facilities such as one described above, for example, a loop-shaped primary path and secondary paths are provided as the travel paths where each secondary path extends along, or by way of, a plurality of article transport locations and is connected to the primary path such that article transport vehicles can diverge from and converge into the primary path. And the secondary paths are spaced apart from each other in the travel direction of the article transport vehicles as they travel along the primary path, and are provided outside and on both lateral sides of the primary path. (See, for example, Patent Document 1.)
Articles are sometimes transported from a secondary path on one side of the primary path to a secondary path on the other side in the facility that includes such primary path and secondary paths. In such cases, an article transport vehicle would travel along the primary path after converging into the primary path from the secondary path on one side, and would have to travel along the loop-shaped primary path to the diverging location into the secondary path located on the other side of the primary path, which results in an increased travel distance for the article transport vehicle. Therefore, transporting of articles cannot be performed efficiently, which leads to a reduction in the transport capacity. In addition, because other article transport vehicles also travel along the primary path and the secondary paths, the area covered by an article transport vehicle may interfere with the areas covered by other article transport vehicles as the distances traveled by the article transport vehicles increase. Thus, it becomes impossible for the article transport vehicle to travel smoothly due to restrictions imposed by other traveling article transport vehicles. Therefore, transport capacity can be reduced as the travel distances of the article transport vehicles increase also for this reason.
To this end, in the facility described in Patent Document 1 described above, transport conveyers are provided, each of which can transport an article between an article transport vehicle in a secondary path on one side of the primary path and an article transport vehicle in a secondary path on the other side of the primary path. This allows articles to be transported from a secondary path on one side of the primary path to a secondary path on the other side by transporting the articles with the transport conveyer while preventing increase in the distances traveled by the article transport vehicles. More specifically, an article is transferred from the article transport vehicle in the secondary path on the one side to the transport conveyer. The article is then transported by the transport conveyer to another secondary path on the opposite side of the primary path. And the article transport vehicle in the secondary path on the other side transports the article to a desired location after receiving the article transported by the transport conveyer.